Field of the Invention
Exemplary embodiments of the present invention relate to a gear actuator for a double clutch transmission, and more particularly, to a gear actuator that performs select and shift operations in a double clutch transmission.
Description of the Related Art
A double clutch transmission (DCT) is a type of automated manual transmission (AMT) that enables gear shifting operations (select and shift operations) of a manual transmission to be automatically performed, and includes actuators for individual shifting operations of respective odd and even-numbered stage gears and controllers to control the operations of the actuators.
FIG. 1 is a back view illustrating a conventional gear actuator, FIG. 2 is a perspective view illustrating a control shaft assembly as one component of the conventional gear actuator, and FIG. 3 is a perspective view illustrating a housing as one component of the conventional gear actuator.
Referring to FIGS. 1 to 3, the conventional gear actuator for a DCT includes an odd-numbered stage select solenoid 1, an odd-numbered stage shift motor 2, an even-numbered stage select solenoid 3, an even-numbered stage shift motor 4, a control shaft assembly 5 that is mechanically connected to the solenoids and the motors to select and shift the lug of a shift rail, and a housing 6 equipped with the components.
In addition, the solenoids 1 and 3 and the motors 2 and 4 are connected to controllers (not shown) through respective individual wirings 7a, 7b, 8a, and 8b for supply of electric power and transmission of control signals. The solenoid-side wirings 7a and 7b are integrated into one component and the motor-side wirings 8a and 8b are integrated into one component so that the integrated components are respectively connected to the controllers through connectors 7c and 8c. 
Accordingly, the associated solenoids and motors are operated by the respective odd and even-numbered stage controllers so that one of odd and even-numbered stage shift lugs is selected and shifted for gear shifting.
Meanwhile, the conventional gear actuator has a problem in that, since all of odd and even-numbered stage select solenoids, shift motors, and controllers are provided as individual parts, it takes a long time to test these parts, an assembly process is complicated, a man-hour for assembly is increased, and an assembly quality is deteriorated.
In addition, since a plurality of wirings 7a, 7b, 8a, and 8b and connectors 7c and 8c are used to connect the select solenoids and the shift motors to the controllers, a connection failure such as a welding defect often occurs in the connection portion between the wirings and the connectors, thereby causing poor transmission of electrical signals (control signals). Hence, there is a problem in that the operating stability of the gear actuator is deteriorated.
In addition, the conventional gear actuator is configured such that the rotational force of the shift motor is transmitted through a reduction gearing to a lead screw to transmit a shift operating force to the control shaft assembly by the nut of the lead screw. In this case, if the gears of the reduction gearing are misaligned, operating noise may be caused and the gear actuator may not operate when low current is supplied thereto. In addition, since the lead screw itself has low operation efficiency, the power consumption of the shift motor is increased, which may lead to a reduction of fuel efficiency.
Meanwhile, the control shaft assembly 5 of the gear actuator has a double shaft structure in which an odd-numbered stage control shaft 5a overlaps with an even-numbered stage control shaft 5b, as illustrated in FIG. 2. Shift finger members 5aa and 5ba are fixed to the upper portions of the respective control shafts 5a and 5b and control finger members 5ab and 5bb are fixed to the lower portions of the respective control shafts 5a and 5b. A pair of select guides 5aa′ protrude from one side of the shift finger member 5aa while a shift finger 5aa″ protrudes from the other side thereof, and a pair of select guides 5ba′ protrude from one side of the shift finger member 5ba while a shift finger 5ba″ protrudes from the other side thereof. Since the select guides 5aa′ and 5ba′ and the shift fingers 5aa″ and 5ba″ are formed in opposite directions to operate the control shafts 5a and 5b in a select direction (axial direction) and a shift direction (circumferential direction), the select solenoids 1 and 3 and the shift motors 2 and 4 to transmit an operating force to them are separately arranged in opposite directions with respect to the control shaft assembly 5. That is, the odd-numbered stage select solenoid 1 and shift motor 2 are disposed to be separated from each other and the even-numbered stage select solenoid 3 and shift motor 4 are disposed to be separated from each other. For this reason, there is a problem in that the arrangement of the select solenoids and the shift motors is complicated and thus the structure of the wirings is complicated. Reference numerals 5ab and 5bb refer to an odd-numbered stage control finger member and an even-numbered stage control finger member that are fixed to the lower portions of the respective control shafts 5a and 5b, and reference numerals 5ab′ and 5bb′ refer to control fingers protruding from the control finger members. The control fingers are parts that allow desired gear shifting by finally pushing or pulling the lug of the shift rail by the shift and select operations.
Meanwhile, in the gear actuator, the select solenoids 1 and 3 allow the select guides 5aa′ and 5ba′ of the respective control shafts to be operated in the select direction (in the vertical direction which is the axial direction in the drawing) through an L-shaped select lever that is hinge-pivoted about the bent portion thereof. The select lever is installed in the housing so as to be pivotable about a hinge shaft. One end of the select lever is connected to the select rod of the select solenoid and the other end of the select lever is inserted between the select guides 5aa′ and 5ba′. To assemble this select lever, a rectangular assembly window 6a as an opening is formed in the upper portion of the housing 6, and the assembly window 6a is provided with a top cover 6b to seal the assembly window after the assembly of the select lever. The housing 6 is disadvantageous in that it has a complicated structure since the assembly window 6a is formed and the top cover 6b is installed in the housing 6. Moreover, there is a problem in that, since the mounting surface and bolt holes for a connector bracket 9, which fixes the connectors of the wirings, must be formed in the housing 6, the housing 6 has a more complicated structure and a man-hour for assembly is increased.
In addition, in the conventional gear actuator, a detent mechanism for maintaining a select position is formed in the select solenoid. However, it is necessary to adjust the assembly position of the select solenoid to accurately fix the select position by a cumulative tolerance for assembly of select-related parts in the gear actuator, and thus a shim is used to adjust and fix the assembly position of the select solenoid. Accordingly, since it is necessary to select and assemble a shim having an appropriate thickness during the assembly of the select solenoid in the related art, there is a problem in that the assembly of the gear actuator is more complicated and the time required to assemble the gear actuator is increased.